Biological Molecules

Question 1

How does hydrogen bonding occurs in water?

Answer 1

The partially positive hydrogens of one water molecule are electrically attracted to the partially negative oxygen atom of another water molecule.

Question 2

what are the properties of water?

Answer 2

1.In metabolic processes

2.As a solvent

3.High latent heat of vaporisation

4.High specific heat capacity

5.Cohesion

6.Adhesion

7.Density

Question 3

What does condensation reactions form?

Answer 3

Dipeptides and polypeptides

Question 4

How many common amino acids are present in living organisms?

Answer 4

20

Question 5

Outline the three condensation reactions of disaccharides ?

Answer 5

1.Maltose forms two a-glucose molecules
2.Sucrose forms a-glucose and fructose
3.Lactose forms b-glucose and galactose

Question 6

What is glucose?

Answer 6

a monosaccharide containing six
carbon atoms in each molecule, it is the main
use for respiration

Question 7

what is starch ?

Answer 7

stores energy in plants (starch grains) and is a mixture of amylose and amylopectin

Question 8

What is amylose?

Answer 8

an unbranched chain of glucose molecules joined by 1, 4
glycosidic bonds, as a result of that amylose is coiled and thus it is a very compact
molecule meaning it can store a lot of energy

Question 9

What is amylopectin?

Answer 9

branched and is made up of glucose molecules joined by 1, 4 and 1,
6 glycosidic bonds, due to the presence of many side branches it is rapidly digested
by enzymes therefore energy is released quickly.

Question 10

What is glycogen?

Answer 10

1.main energy storage molecule in animals

2.formed from many
molecules of alpha glucose joined together by 1, 4 and 1, 6 glycosidic bonds

3.large number of side branches meaning that glucose & therefore energy, can be released quickly.

4.large but compact molecule thus maximising the amount of
energy it can store

Question 11

What is cellulose?

Answer 11

cells walls in plants
long, unbranched chains of beta glucose joined by glycosidic bonds.

Microfibrils made of long cellulose chains joined together by hydrogen bonds

provide structural support in plants cells.

Question 12

What are lipids?

Answer 12

are biological molecules which are only soluble in organic solvents such as alcohols.

Question 13

What is the difference between saturated and unsaturated lipids?

Answer 13

Saturated lipids are found in animal fats and don’t contain c-c double bonds whereas unsaturated lipids are found in plants and contains c-c double bonds.

Question 14

The greater the number of unsaturated bonds….

Answer 14

….the weaker the intermolecular bonds resulting
in lower melting point.

so unsaturated lipids are liquid at room temp compared to saturated lipids that are solid at room temp

Question 15

What are triglycerides?

Answer 15

1. are lipids made of one molecule of
   glycerol and three fatty acids joined by ester
   bonds formed in condensation reactions
2. used as
   energy reserves in plant and animal cells.

Question 16

What are phospholipids?

Answer 16

1. a glycerol molecule, two fatty acids, and a phosphate group

2.Phosphate heads are hydrophilic and the tails are hydrophobic and as a

3. form micelle or bilayer

Question 17

What is the difference between reducing and non-reducing sugars?

Answer 17

Reducing= electron donor

Non-reducing= electron acceptor

Question 18

Outline the benedict’s test for reducing sugars

Answer 18

Add Benedict’s solution.

Heat the mixture.

Observe the colour change- should form a red precipitate

Benedict’s Test is semi-quantitative.

Question 19

Outline the benedict’s test for non-reducing sugars

Answer 19

If theres no colour change then you must:

Add dilute hydrochloric acid, then neutralise.

Heat and observe colour change- blue brick red

Question 20

Outline the Biuret test- Test for proteins

Answer 20

1. a sample placed in a test tube
2. NaOH is added.
3. few drops of dilute copper (II) sulfate solution is added mixed.
4. In the presence
   of a protein, the solution turns lilac/ as an indicator of peptide bonds.

5.In the absence of protein, the solution remains blue

Question 21

Outline the emulsion test- test for lipids

Answer 21

1. 2ml of sample is added to 5ml of ethanol
2. contents are mixed by shaking to ensure that
   the lipids dissolved.
3. add 5ml of water
   solution turns
   cloudy indicating the presence of lipid due to the formation of an emulsion

Question 22

Outline the Iodine test for starch.

Answer 22

in the presence of starch, the colour of
potassium iodide solution from yellow to black/blue.

Question 23

What is the primary structure?

Answer 23

protein is the order and number of amino acids in a protein.

Question 24

What is the secondary structure?

Answer 24

either
alpha helix or beta pleated sheet. The shape is determined by the hydrogen
bonding.

Question 25

What is the tertiary structure?

Answer 25

3D shape of the protein- with ionic,disulfide, hydrophobic forces and hydrogen bonds

Question 26

What is the quaternary structure?

Answer 26

final 3D structure with same bonds in tertiary

Question 27

what are globular proteins?

Answer 27

spherical
soluble in water

Question 28

examples of globular proteins.

Answer 28

Haemoglobin- two alpha and
two beta polypeptide chains each containing a haem group made of iron

Question 29

what are fibrous proteins?

Answer 29

strength and support

Question 30

examples of fibrous proteins.

Answer 30

collagen- strong protein due to the types of bonds in its structure, e.g h-bonds and covalent bonds